1. Field of the Invention
This invention relates to a circuit for use in a display, a printer or the like, which is adapted to realize the region filling algorithm of a character pattern and a figure pattern composed of dots by hardware.
2. Description of Related Art
Conventionally, a region in a character pattern and a figure pattern has been filled according to a plurality of region filling algorithms by means of software (Japanese Patent laid-Open Application Nos. 1-237775 (1989)), 2-45889 (1990) and Japanese Patent Publication No. 53-41017 (1978).
FIG. 1 is a flow chart of an example of the region filling algorithm.
The coordinate of pixel in the plotting region of a screen etc. is computed (S1), based on which both the starting address of a memory for storing the data of the filling region and the bit data for the first filling are formed while from the bit at the plotting starting position to the least significant bit in the filling area sectioned for every word or the like is rendered "1" (S2).
In the first filling, the bit data for the first filling obtained in the step S2 and the data of the starting address of the memory area where the bit data of the pattern to be filled is stored are subjected to an exclusive OR operation, thereby to perform filling (S3).
It is detected whether the memory address corresponding to the filling region is the filling end address (S4). If the memory address is the end address, the filling is terminated, whereas if the memory address has not reached the end address, the filling of a next area is conducted (S5).
The bit data for the second filling and afterwards is set to be al "1". The filling is achieved by performing an exclusive OR operation of the bit data of the second filling and afterwards and the data of a next address to the storing area of the first filling data.
As described above, in the conventional method to realize the region filling algorithm by means of software, the filling should be repeatedly carried out by software, thus taking a long time for the filling.
Although Japanese Patent, Application Laid-Open No. 4-50896 (1992) reveals a plotting circuit which realizes the region filling algorithm as above by hardware, the plotting circuit requires a process to develop the outline data turned from a vector to a dot image by a CPU.